Fluid loss additive for oil-based muds

ABSTRACT

A composition that includes a product resulting from a condensation reaction of quebracho with at least one organophilic species that includes a reactive amine is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application, pursuant to 35 U.S.C. §119(e), claims priority to U.S.Patent Application No. 60/806,749, filed Jul. 7, 2006, which is hereinincorporated by reference in its entirety.

BACKGROUND OF INVENTION

1. Field of the Invention

Embodiments disclosed herein relate generally to components of wellborefluids (muds). More specifically, embodiments relate to fluid lossadditives used in oil-based muds.

2. Background Art

When drilling or completing wells in earth formations, various fluidstypically are used in the well for a variety of reasons. Common uses forwell fluids include: lubrication and cooling of drill bit cuttingsurfaces while drilling generally or drilling-in (i.e., drilling in atargeted petroliferous formation), transportation of “cuttings” (piecesof formation dislodged by the cutting action of the teeth on a drillbit) to the surface, controlling formation fluid pressure to preventblowouts, maintaining well stability, suspending solids in the well,minimizing fluid loss into and stabilizing the formation through whichthe well is being drilled, fracturing the formation in the vicinity ofthe well, displacing the fluid within the well with another fluid,cleaning the well, testing the well, transmitting hydraulic horsepowerto the drill bit, fluid used for emplacing a packer, abandoning the wellor preparing the well for abandonment, and otherwise treating the wellor the formation.

In most rotary drilling procedures the drilling fluid takes the form ofa “mud,” i.e., a liquid having solids suspended therein. The solidsfunction to impart desired rheological properties to the drilling fluidand also to increase the density thereof in order to provide a suitablehydrostatic pressure at the bottom of the well. The drilling mud may beeither a water-based or an oil-based mud.

Many types of fluids have been used in well bores particularly inconnection with the drilling of oil and gas wells. The selection of anoil-based well bore fluid involves a careful balance of both the goodand bad characteristics of such fluids in a particular application. Theprimary benefits of selecting an oil-based drilling fluid include:superior hole stability, especially in shale formations; formation of athinner filter cake than the filter cake achieved with a water basedmud; excellent lubrication of the drilling string and downhole tools;penetration of salt beds without sloughing or enlargement of the hole aswell as other benefits that should be known to one of skill in the art.An especially beneficial property of oil-based muds is their excellentlubrication qualities. These lubrication properties permit the drillingof wells having a significant vertical deviation, as is typical ofoff-shore or deep water drilling operations or when a horizontal well isdesired. In such highly deviated holes, torque and drag on the drillstring are a significant problem because the drill pipe lies against thelow side of the hole, and the risk of pipe sticking is high when waterbased muds are used. In contrast oil-based muds provide a thin, slickfilter cake which helps to prevent pipe sticking and thus the use of theoil-based mud can be justified.

Drilling fluids are generally characterized as thixotropic fluidsystems. That is, they exhibit low viscosity when sheared, such as whenin circulation (as occurs during pumping or contact with the movingdrilling bit). However, when the shearing action is halted, the fluidshould be capable of suspending the solids it contains to preventgravity separation. In addition, when the drilling fluid is under shearconditions and a free-flowing near-liquid, it must retain a sufficientlyhigh enough viscosity to carry all unwanted particulate matter from thebottom of the well bore to the surface. The drilling fluid formulationshould also allow the cuttings and other unwanted particulate materialto be removed or otherwise settle out from the liquid fraction.

There is an increasing need for drilling fluids having the rheologicalprofiles that enable wells to be drilled more easily. Drilling fluidshaving tailored rheological properties ensure that cuttings are removedfrom the wellbore as efficiently and effectively as possible to avoidthe formation of cuttings beds in the well which can cause the drillstring to become stuck, among other issues. There is also the need froma drilling fluid hydraulics perspective (equivalent circulating density)to reduce the pressures required to circulate the fluid, reducing theexposure of the formation to excessive forces that can fracture theformation causing the fluid, and possibly the well, to be lost. Inaddition, an enhanced profile is necessary to prevent settlement or sagof the weighting agent in the fluid, if this occurs it can lead to anuneven density profile within the circulating fluid system which canresult in well control (gas/fluid influx) and wellbore stabilityproblems (caving/fractures).

To obtain the fluid characteristics required to meet these challengesthe fluid must be easy to pump, so it requires the minimum amount ofpressure to force it through restrictions in the circulating fluidsystem, such as bit nozzles or down-hole tools. In other words the fluidmust have the lowest possible viscosity under high shear conditions.Conversely, in zones of the well where the area for fluid flow is largeand the velocity of the fluid is slow or where there are low shearconditions, the viscosity of the fluid needs to be as high as possiblein order to suspend and transport the drilled cuttings. This alsoapplies to the periods when the fluid is left static in the hole, whereboth cuttings and weighting materials need to be kept suspended toprevent settlement. However, it should also be noted that the viscosityof the fluid should not continue to increase under static conditions tounacceptable levels. Otherwise when the fluid needs to be circulatedagain this can lead to excessive pressures that can fracture theformation or lead to lost time if the force required to regain a fullycirculating fluid system is beyond the limits of the pumps.

Further, it is also important that a drilling possess the ability toresist filtration. To prevent formation fluids from entering thewellbore hole, the hydrostatic pressure of the mud column must begreater than the pressure of the fluids in the pores of the formation.As a result, there is a tendency for the liquid portion of wellborefluids to invade the permeable wellbore formations, which is referred toas the filtrate. As a result, the mud solids are filtered out onto thewalls of the wellbore hole, forming a coating or cake. Thus, the mudsmust be formulated so as to keep the deposited cake permeability as lowas possible in order to maintain a stable borehole and minimize filtrateinvasion of, and damage to, potentially productive strata and horizonsin the production formation. The loss of filtrate to the formation isreferred to as fluid loss.

In addressing issues surrounding fluid loss control, one must chooseadditives that are compatible with the solvent system of the mud.Oil-based muds frequently use invert emulsions with a mixture of oil andwater in the presence of surfactants. Fluid loss control materialstypically used in drilling muds include plant tannins, such as thosefound in the wood of quebracho, chestnut, oak and urunday, and in thebark of wattle, mangrove, oak, eucalyptus, hemlock, pine, larch, andwillow trees. Other materials include starches (e.g. corn, potato),starch derivatives, water soluble cellulose derivatives, humates,polyphosphates or phosphate-containing materials, lignite materials,lignosulfonates and synthetic polymers (especially swellable polymersand gels).

Many of these polymers and condensed-tannin materials are either watersoluble or at least hydrophilic and thus benefit from chemicalmodification to impart organophilic character when used in conjunctionwith oil/invert emulsion-based muds. For example, U.S. Pat. No.4,421,655 discloses the use of humates modified with amido amines in thepresence of polyvalent metal ion. U.S. Pat. No. 4,710,586 discloses theuse of alkyl quaternary ammonium salts reacted with quebracho for use asfluid loss additives. Another consideration is the use of materials thatare environmentally compatible

The materials that affect the rheological profile of oil-based muds mayinclude both viscosifiers and fluid loss additives. Accordingly, thereexists a continuing need for improving these drilling materials andwellbore fluid formulations.

SUMMARY OF INVENTION

In one aspect, embodiments disclosed herein relate to a composition thatincludes a product resulting from a condensation reaction of quebrachowith at least one organophilic species that includes a reactive amine.

In another aspect, embodiments disclosed herein relate to an invertemulsion drilling fluid that includes an oleaginous continuous phase, anon-oleaginous discontinuous phase, an emulsifier present in an amountsufficient to stabilize the invert emulsion and a quebracho-basedadditive resulting from a condensation reaction of quebracho and atleast one organophilic species that includes a reactive amine.

In yet another aspect, embodiments disclosed herein relate to a methodof drilling a subterranean hole with an invert emulsion drilling fluid,which includes mixing an oleaginous fluid, a non-oleaginous fluid, anemulsifier, and a quebracho-based additive resulting from a condensationreaction of quebracho and an organophilic species that includes areactive amine, to form an invert emulsion and drilling the subterraneanhole using this invert emulsion as the drilling fluid.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

DETAILED DESCRIPTION

Embodiments disclosed herein relate to fluid loss additives in wellborefluid mud formulations. In particular, some embodiments disclosed hereinrelate to fluid loss additives which are condensation reaction productsof quebracho and lipophilic amines. In the following description,numerous details are set forth to provide an understanding of thepresent invention. However, it will be understood by those skilled inthe art that the present invention may be practiced without thesedetails and that numerous variations or modifications from the describedembodiments may be possible.

Fluid Loss Additive

In one embodiment, a composition for a fluid loss additive comprises acondensation reaction product of quebracho and an organophilic specieshaving a reactive amine. As used herein, a “reactive amine” comprisesany amine having at least one active hydrogen, i.e., primary orsecondary amines, which are able to react with quebracho in acondensation reaction.

In one embodiment the organophilic reactive amine may comprise C₆-C₂₂fatty acid amines. Such amines may be derived by standard proceduresfrom fatty acids including, for example, lauric acid, myristic acid,palmitic acid, stearic acid, oleic acid, or linoleic acid. Other naturallong chain amines such as tallow amine may be reacted with quebracho. Inone embodiment, the organophilic reactive amine may include any C₆-C₂₂alkyl amine or polyamine such as an amine that has the formula H₂NR,where R is an alkyl chain having 6 to 22 carbons. The carbon chain(s)may be branched or straight chain alkyls, which may be substitutedalkyls. One of ordinary skill in the art would recognize that bysubstituted one means replacing a hydrogen along the alkyl chain withany other atom or group of atoms, including isotopes such as deuterium.

In another embodiment, the organophilic reactive amine may comprise atleast one of a polyamine surfactant and an amidoamine surfactant.Amidoamine surfactants suitable that may be reacted with quebrachoinclude those represented by:

wherein R₁ is selected from a C₁₂-C₃₀ alkyl, C₁₂-C₃₀ alkenyl, C₁₂-C₃₀arylalkyl, and C₁₂-C₃₀ cycloalkyl; R₂ and R₃ are each independentlyselected from H or a C₁-C₄ alkyl; R₄ and R₅ are each independentlyselected from H, C₁-C₄ alkyl, C₁-C₄ alkoxyalkyl, and C₁-C₄ hydroxyalkyl;and n is an integer from 1 to 10. Amidoamines may be formed from thereaction of a polyamine with a carboxylic acid. For example, in aparticular embodiment, an amidoamine formed from a C₆-C₂₂ fatty acidreacted with a polyamine. In a particular embodiment, the organophilicreactive amine may include a C₁₂-C₂₂ fatty acid reacted with apolyalkylene polyamine. Alternatively, the organophilic reactive aminemay include 2-alkyl imidazoline formed from C₁₂-C₂₂ fatty acid reactedwith a polyalkylene polyamine, which may then be derivatized with adicarboxylic acid. Such 2-alkyl imidazoline derivatives are describedfor example in U.S. Pat. No. 4,544,756, which is herein incorporated byreference in its entirety.

In a particular embodiment, SUREMUL®, an amidoamine surfactant that iscommercially available from M-I L.L.C. (Houston, Tex.), may be reactedwith quebracho to form a quebracho-amine reaction product as disclosedherein. Polyamines suitable to be reacted with quebracho include linearor branched organophilic C₆-C₃₆ fatty polyamines including polyaliphaticpolyamines, heterocyclic polyamines, and alkylalkanol polyamines. In oneembodiment, organophilic reactive polyamines may have at least one aminebeing a reactive amine. Alternatively, an organophilic speciescomprising a tertiary amine may be reacted with quebracho.

Formation of the Fluid Loss Additives

To form the reaction products of quebracho and an organophilic reactiveamine disclosed herein, the organophilic reactive amine may be slowlymixed with the desired amount of finely divided quebracho, and mixed forabout 15 minutes in a Warring blender or ground in a mortar and pestle.The mixture may be heated to initiate a condensation reaction betweenquebracho and the organophilic reactive amine. The condensation reactionproducts may be dried and ground again to a fine powder. On a commercialscale, any conventional high intensity mixer may be used, such as a pugmill, Littleford mixer, and the like. After drying and grinding, thequebracho-amine condensation reaction product may be readily dispersedin the oil base drilling mud formulation by mixing or stirring; or thequebracho-amine reaction product may be added at any stage of theformulations of the oil base mud compositions.

In one embodiment, the condensation reaction of quebracho with theorganophilic reactive amine may require the application of externalheating. In a particular embodiment, the reaction may occur in atemperature range from about 100 to 350° F., and from about 175 to about275° F. in another embodiment.

In another embodiment, the weight percent ratio of quebracho to theorganophilic reactive amine may range from about 50:50 to about 95:5,from about 66:34 to about 90:10 in another embodiment, and from about75:25 to 80:15 in yet another embodiment.

In yet another embodiment, the quebracho-amine reaction product may befinely ground to a particle size in a range from 10 mesh to 400 mesh USStandard, such that at least 50 weight percent passes a 20 mesh screen.In another embodiment, the quebracho-amine reaction product may befinely ground to a particle size in a range from 10 to 50 mesh, and in arange from about 15 to 25 mesh in yet another embodiment.

Invert Emulsion Fluids and Method of Drilling

In one embodiment, the quebracho-amine reaction products disclosedherein may be included in a wellbore fluid. The wellbore fluids mayinclude, for example, an oleaginous continuous phase, a non-oleaginousdiscontinuous phase, a quebracho-amine reaction product weightingagents, emulsifiers, and/or viscosifiers.

The oleaginous fluid may be a liquid and more preferably is a natural orsynthetic oil and more preferably the oleaginous fluid is selected fromthe group including diesel oil; mineral oil; a synthetic oil, such ashydrogenated and unhydrogenated olefins including polyalpha olefins,linear and branch olefins and the like, polydiorganosiloxanes,siloxanes, or organosiloxanes, esters of fatty acids, specificallystraight chain, branched and cyclical alkyl ethers of fatty acids,mixtures thereof and similar compounds known to one of skill in the art;and mixtures thereof. The concentration of the oleaginous fluid shouldbe sufficient so that an invert emulsion forms and may be less thanabout 99% by volume of the invert emulsion. In one embodiment the amountof oleaginous fluid is from about 30% to about 95% by volume and morepreferably about 40% to about 90% by volume of the invert emulsionfluid. The oleaginous fluid in one embodiment may include at least 5% byvolume of a material selected from the group including esters, ethers,acetals, dialkylcarbonates, hydrocarbons, and combinations thereof.

The non-oleaginous fluid used in the formulation of the invert emulsionfluid disclosed herein is a liquid and preferably is an aqueous liquid.More preferably, the non-oleaginous liquid may be selected from thegroup including sea water, a brine containing organic and/or inorganicdissolved salts, liquids containing water-miscible organic compounds andcombinations thereof. The amount of the non-oleaginous fluid istypically less than the theoretical limit needed for forming an invertemulsion. Thus in one embodiment the amount of non-oleaginous fluid isless that about 70% by volume and preferably from about 1% to about 70%by volume. In another embodiment, the non-oleaginous fluid is preferablyfrom about 5% to about 60% by volume of the invert emulsion fluid. Thefluid phase may include either an aqueous fluid or an oleaginous fluid,or mixtures thereof. In a particular embodiment, various weightingagents may be included in a wellbore fluid.

Conventional methods can be used to prepare the drilling fluidsdisclosed herein in a manner analogous to those normally used, toprepare conventional oil-based drilling fluids. In one embodiment, adesired quantity of oleaginous fluid such as a base oil and a suitableamount of a surfactant are mixed together and the remaining componentsare added sequentially with continuous mixing. An invert emulsion mayalso be formed by vigorously agitating, mixing or shearing theoleaginous fluid and the non-oleaginous fluid.

The amounts of the quebracho-amine reaction product used in the drillingfluid formulations may vary from about 1 pound per barrel of oil basedrilling muds to about 20 pounds per barrel in one embodiment; from 3 to16 pounds per barrel in another embodiment; and from 6 to 12 pounds perbarrel in yet another embodiment. One of ordinary skill in the art wouldrecognize that more than about 16 pounds per barrel increases costs andmay not be necessary, although more can be used as needed.

Other additives that may be included in the wellbore fluids disclosedherein include for example, wetting agents, organophilic clays,viscosifiers, surfactants, dispersants, interfacial tension reducers, pHbuffers, mutual solvents, thinners, thinning agents and cleaning agents.The addition of such agents should be well known to one of ordinaryskill in the art of formulating drilling fluids and muds.

Emulsifiers that may be used in the fluids disclosed herein include, forexample, fatty acids, soaps of fatty acids, amidoamines, polyamides,polyamines, oleate esters, such as sorbitan monoleate, sorbitandioleate, imidazoline derivatives or alcohol derivatives andcombinations or derivatives of the above. Additionally, lime or otheralkaline materials are typically added to conventional invert emulsiondrilling fluids and muds to maintain a reserve alkalinity.

Wetting agents that may be suitable for use in the fluids disclosedherein include crude tall oil, oxidized crude tall oil, surfactants,organic phosphate esters, modified imidazolines and amidoamines, alkylaromatic sulfates and sulfonates, and the like, and combinations orderivatives of these. However, when used with the invert emulsion fluid,the use of fatty acid wetting agents should be minimized so as to notadversely affect the reversibility of the invert emulsion disclosedherein. FAZE-WET™, VERSACOAT™, SUREWET™, VERSAWET™, and VERSAWET™ NS areexamples of commercially available wetting agents manufactured anddistributed by M-I L.L.C. that may be used in the fluids disclosedherein. Silwet L-77, L-7001, L7605, and L-7622 are examples ofcommercially available surfactants and wetting agents manufactured anddistributed by General Electric Company (Wilton, Conn.).

Organophilic clays, normally amine treated clays, may be useful asviscosifiers and/or emulsion stabilizers in the fluid compositiondisclosed herein. Other viscosifiers, such as oil soluble polymers,polyamide resins, polycarboxylic acids and soaps can also be used. Theamount of viscosifier used in the composition can vary upon the end useof the composition. However, normally about 0.1% to 6% by weight rangeis sufficient for most applications. VG-69™ and VG-PLUS™ are organoclaymaterials distributed by M-I, L.L.C., Houston, Tex., and VERSA-HRP™ is apolyamide resin material manufactured and distributed by M-I, L.L.C.,that may be used in the fluids disclosed herein. In some embodiments,the viscosity of the displacement fluids is sufficiently high such thatthe displacement fluid may act as its own displacement pill in a well.

Conventional suspending agents that may be used in the fluids disclosedherein include organophilic clays, amine treated clays, oil solublepolymers, polyamide resins, polycarboxylic acids, and soaps. The amountof conventional suspending agent used in the composition, if any, mayvary depending upon the end use of the composition. However, normallyabout 0.1% to about 6% by weight is sufficient for most applications.VG-69™ and VG-PLUS™ are organoclay materials distributed by M-I L.L.C.,and VERSA-HRP™ is a polyamide resin material manufactured anddistributed by M-I L.L.C., that may be used in the fluids disclosedherein.

Weighting agents or density materials suitable for use the fluidsdisclosed herein include galena, hematite, magnetite, iron oxides,illmenite, barite, siderite, celestite, dolomite, calcite, and the like.The quantity of such material added, if any, depends upon the desireddensity of the final composition. Typically, weight material is added toresult in a drilling fluid density of up to about 24 pounds per gallon.The weight material is preferably added up to 21 pounds per gallon andmost preferably up to 19.5 pounds per gallon.

In one embodiment, a method of drilling a subterranean hole with aninvert emulsion drilling fluid comprises mixing an oleaginous fluid, anon-oleaginous fluid, an emulsifier, and a quebracho-amine condensationreaction product to form an invert emulsion; and drilling thesubterranean hole using this invert emulsion as the drilling fluid. Thefluid may be pumped down to the bottom of the well through a drill pipe,where the fluid emerges through ports in the drilling bit, for example.In one embodiment, the fluid may be used in conjunction with anydrilling operation, which may include, for example, vertical drilling,extended reach drilling, and directional drilling. One skilled in theart would recognize that oil-based drilling muds may be prepared with alarge variety of formulations. Specific formulations may depend on thestate of drilling a well at a particular time, for example, depending onthe depth and/or the composition of the formation. The drilling mudcompositions described above may be adapted to provide improvedoil-based drilling muds under conditions of high temperature andpressure, such as those encountered in deep wells.

The fluids disclosed herein are especially useful in the drilling,completion and working over of subterranean oil and gas wells. Inparticular the fluids disclosed herein may find use in formulatingdrilling muds and completion fluids that allow for the easy and quickremoval of the filter cake. Such muds and fluids are especially usefulin the drilling of horizontal wells into hydrocarbon bearing formations.

EXAMPLES

The following examples were used to test the effectiveness ofquebracho-amine reaction products disclosed herein as fluid lossadditives.

Tested fluid loss agents were formed as follows: 1) Additive A: 55 g ofQuebracho was thoroughly mixed with 15 g of fatty acid derived amineusing mortar and pestle and the mixture was subjected to 225° F. for16-20 h. The product so obtained was finely powdered using a mixer andscreened using #20 meshes and used as fluid loss control agent; 2)Additive B: 55 g of TANNATHIN® was thoroughly mixed with 15 g of fattyacid derived amine using mortar and pestle and the mixture was subjectedto 225° F. for 16-20 h. The product so obtained was finely powderedusing a mixer and screened using #20 meshes and used as fluid losscontrol agent; and 3) Additive C: 300 g of powdered Quebracho wasthoroughly mixed with SUREMUL® (75 g) using mortar and pestle and themixture was subjected to 225° F. for 16-20 h. The product so obtainedwas finely powdered using a mixer and screened using #20 meshes and usedas fluid loss control agent.

The fluid loss additives (Additives A, B, and C) were included in invertemulsion fluids formulated with IO 1618 as the base oil (synthetic oilcomposed of C₁₆-C₁₈ internal olefins) and water in an approximate ratioof 65:35 and various additives. Referring to Tables 1a and 1b below, thecomponents included in invert emulsion fluid Samples 1-13 are shown.

TABLE 1a Mud Compositions (quantities in pounds per barrel) Sample # 1 23 4 5 6 7 Components bbl bbl bbl bbl bbl bbl bbl IO 1618 143.81 143.81143.81 143.81 143.11 143.81 143.81 CaCl₂ 27.73 27.73 27.73 27.73 21.4627.73 27.73 Water 77.63 77.63 77.63 77.63 60.08 77.63 77.63 Lime 4.004.00 4.00 4.00 4.00 4.00 4.00 Organo Clay 4.00 4.00 4.00 4.00 4.00 VGPlus ® 4.00 4.00 SUREMUL ® 10.00 10.00 10.00 10.00 12.00 12.00 12.00SUREWET ® 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Fluid Loss Control 10.00 -12.00 - 10.00 - 12.00 - 10.00 - 10.00 - 10.00 - Additive A Additive AAdditive B Additive B Additive A Additive A Additive C RHETHIK ® — — — —0.50 0.00 0.50 Rev. Dust 20.00 20.00 20.00 20.00 20.00 20.00 20.00Barite 209.83 209.83 209.83 209.83 209.83 209.83 209.83 Aging Temp. 300°F. 300° F. 300° F. 300° F. 350° F. 350° F. 350° F.

TABLE 1b Mud Composition (quantities in pound per barrel) Sample # 8 910 11 12 13 Components bbl bbl bbl bbl bbl bbl IO 1618 143.81 143.11143.11 147.94 147.94 147.94 CaCl₂ 27.73 21.46 21.46 16.64 16.64 16.64Water 77.63 60.08 60.08 46.59 46.59 46.59 Lime 4.00 4.00 4.00 4.00 4.004.00 VG PLUS ® 8.00 6.00 6.00 8.00 8.00 8.00 SUREMUL ® 12.00 12.0 12.012.0 12.00 12.00 SUREWET ® 4.0 4.0 4.00 4.00 4.00 4.00 Fluid Loss 12.018.0 20.0 20.0 18.00 20.00 Control Quebracho Additive C Additive CAdditive C Additive C Additive C RHETHIK ® 0.50 — — — — — Rev. Dust20.00 15.00 15.00 15.00 15.00 15.00 Barite 209.83 329.35 329.35 335.84335.84 335.84 Aging Temp. 350° F. 350° F. 350° F. 350° F. 375° F. 375°F.

The above invert emulsion drilling fluids were heat aged at thetemperatures shown below in Tables 2a and 2b by hot rolling for 16hours, and the rheological properties of the various mud formulationswere determined using a Fann Model 35 Viscometer, available from FannInstrument Company. The fluid exhibited the following properties, asshown below in Table 2.

TABLE 2 Fluid Rheology at 120° F. Sample 1 2 3 4 5 6 7 8 9 10 11 12 13600 RPM 67 72 85 87 72 74 79 70 92 89 103 114 140 300 RPM 39 39 52 53 4141 48 41 50 48 58 63 75 200 RPM 29 29 40 41 31 29 38 32 36 35 42 46 53100 RPM 18 18 27 28 19 18 26 21 21 21 26 26 31  6 RPM 5 5 10 10 6 5 9 75 5 7 5 6  3 RPM 5 4 9 9 5 4 8 6 3 4 5 3 4 10 s gel 6 6 12 13 5 4 8 7 55 8 6 6 10 m gel 6 6 16 18 7 6 11 9 7 7 15 11 12 PV (cP) 28 33 33 34 3133 31 29 42 41 45 51 65 YP 11 6 19 19 10 8 17 11 8 7 14 12 10 (lb/100ft²) HTHP 2.4 3.2 20.8 17.6 3.2 3.0 3.0 29.0 7.2 6.0 2.8 8.4 11.2 Fluidloss (mL)

The results of the HTHP fluid loss measurements show that quebrachoreacted with fatty acid amines (Samples 1, 2, 5, and 6) or with theamidoamine surfactant, SUREMUL®, (Samples 7, 9-13) are superior relativeto unmodified quebracho (Sample 8) or TANNATHIN®, a lignite, reactedwith fatty acid amines (Samples 3 and 4).

Advantages of the additives and fluids described herein may include atleast one of the following. Fluids incorporating a reaction product ofan organophilic reactive amine and quebracho may allow for enhancedrheological properties of the fluids. Such agents may also increaselubricity and diminish wear of the drilling equipment. Furthermore, thequebracho-amine reaction products described herein may be consideredenvironmentally compatible due to their ready biodegradability.Compositions as described herein may be effectively used as fluid lossagents at temperatures as high as 375 to 450° F. As compared to otherproducts, the fluid loss agents disclosed herein may provide ease ofdispersion into the oil base fluids. Additionally, the formation of thefluid loss additives disclosed herein may not require the presence ofpolyvalent cations and may be substantially free of polyvalent metalliccations.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed:
 1. A composition, comprising: a product resulting froma condensation reaction of quebracho and a C₆-C₂₂ alkyl amine, whereinthe amine has the formula H₂NR, where R is an alkyl chain having 6 to 22carbons.
 2. An invert emulsion drilling fluid, comprising: an oleaginouscontinuous phase; a non-oleaginous discontinuous phase; an emulsifierpresent in an amount sufficient to stabilize the invert emulsion; and aquebracho-based additive resulting from a condensation reaction ofquebracho and a C₆-C₂₂ alkyl amine, wherein the amine has the formulaH₂NR, where R is an alkyl chain having 6 to 22 carbons.
 3. The drillingfluid of claim 2, wherein the C₆-C₂₂ alkyl amine comprises at least onesurfactant.
 4. The drilling fluid of claim 2, wherein the oleaginousfluid comprises from about 30% to less than 100% by volume of thedrilling fluid.
 5. The drilling fluid of claim 2, wherein the oleaginousfluid is selected from diesel oil, mineral oil, synthetic oil, esteroils, glycerides of fatty acids, aliphatic esters, aliphatic ethers,aliphatic acetals, or other such hydrocarbons and combinations thereof.6. The drilling fluid of claim 2, wherein the non-oleaginous fluidcomprises from about 1% to about 70% by volume of said drilling fluid.7. The drilling fluid of claim 2, wherein the non-oleaginous fluid isselected from fresh water, sea water, brine, aqueous solutionscontaining water soluble organic salts, water soluble alcohols or watersoluble glycols or combinations thereof.
 8. The drilling fluid of claim2, further comprising: a weighting agent.
 9. A method of drilling asubterranean hole with an invert emulsion drilling fluid, comprising:mixing an oleaginous fluid, a non-oleaginous fluid, an emulsifier, and aquebracho-based additive resulting from a condensation reaction ofquebracho and a C₆-C₂₂ alkyl amine, wherein the amine has the formulaH₂NR, where R is an alkyl chain having 6 to 22 carbons to form an invertemulsion; and drilling the subterranean hole using said invert emulsionas the drilling fluid.